fix(vmsnapshot): set phase to Pending on SyncFSFreezeRequest errors

[diafour]

Description

• Always set phase on first vmsnapshot reconcile, i.e. after creation.

Why do we need it, and what problem does it solve?

VMSnapshot may stuck in empty phase state on some circumstances, e.g. snapshoting during module update or migration.

Update object with empty phase is forbidden:

{"level":"error","msg":"Failed to update resource","controller":"vmsnapshot-controller","err":"error updating status subresource: VirtualMachineSnapshot.virtualization.deckhouse.io \"vm-snap-alpine-1-repl-repl-p6v2m\" is invalid: status.phase: Unsupported value: \"\": supported values: \"Pending\", \"InProgress\", \"Ready\", \"Failed\", \"Terminating\"","name":"vm-snap-alpine-1-repl-repl-p6v2m","namespace":"default","reconcileID":"47db4b8c-0181-4bee-ad77-7406bddfda21","time":"2026-01-22T15:36:05Z"}

What is the expected result?

• Errors during freeze sync are reported in VMSnapshot status.
• No errors in logs.

Checklist

• The code is covered by unit tests.
• e2e tests passed.
• Documentation updated according to the changes.
• Changes were tested in the Kubernetes cluster manually.

Changelog entries

section: vmsnapshot
type: fix
summary: Fix "unsupported empty phase" errors for VMSnapshot.